Multiple-part curable resins (e.g., epoxides and dental restorative resins) frequently are dispensed and mixed using a multiple-barrelled syringe equipped with an exit nozzle containing a static mixing element. The materials contained in the syringe are dispensed and mixed by depressing the syringe plunger, thereby forcing the resin components from the syringe barrels into the static mixing element (where the resin parts are intermixed with one another) and out the exit nozzle. When it is contemplated that the contents of the syringe will not be completely consumed in one use, the static mixing element and exit nozzle frequently are designed to be detached from the syringe outlet and disposed of after use. In such applications, several detachable and disposable static mixing elements and exit nozzles ordinarily are included with each syringe. After a quantity of curable resin has been dispensed and mixed from the syringe, the used static mixing element and exit nozzle can be detached from the syringe outlet and discarded, and a new static mixing element and exit nozzle fitted to the syringe outlet.
One commercially used double-barrelled dispensing device employs a static mixing element made from a plurality of counter-rotated "bow-tie" or auger-like mixing blades of the type described in U.S. Pat. Nos. 3,286,992 and 3,664,638. Such a static mixing element successively subdivides, rotates, and recombines the incoming resin streams to convert them to a homogeneous, readily curable mass. This dispensing device is referred to by its manufacturer as a "Kenpac" syringe and is described in "Kenpac fail-safe mixer/applicator for production assembly or field repairs", commercial literature of the Kenics Corporation. The "Kenpac" syringe has two barrels, each having a capacity of about 12 cm.sup.3. A disposable eightbladed static mixing element about 6 mm in diameter by about 50 mm long is used with the syringe, together with an exit nozzle which encases the static mixing element and detachably mounts on the syringe outlet. If the degree of mixing offered by the use of a single static mixing element and nozzle is insufficient, additional static mixing elements can be interposed between the exit nozzle and syringe outlet, and are carried in nozzle extension tubes. After use of a portion of the syringe's contents, the used static mixing element(s), exit nozzle, and nozzle extension tubes (if any) can be removed from the syringe outlet and replaced with new components.